Hydraulic dust curtain



April 12, 1966 D. E. HERMAN 3,245,623

HYDRAULIC DUST CURTAIN Filed Dec. 21, 1964 3 Sheets-Sheet 1 M 0 TOR Co/v TRO L (FEVER-SING) fl/ezz/or flonafa Z. 7761022022 April 12, 1966 D.E. HERMAN HYDRAULIC DUST CURTAIN 3 Sheets-Sheet 2 Filed Dec. 21, 1964fi/efizfaf Jana/a Z. ermazz m, Mmx VM (05 TEN r) MANUAL April 12, 1966Filed Dec. 21, 1964 D. E. HERMAN HYDRAULIC DUST CURTAIN MANUAL (oars/vT} 3 Sheets-Sheet 3 Dona/cl E Wermczzz the hammers.

United States Patent 3,245,623 HYDRAULIC DUST CURTAIN Donald E. Herman,Cedar Rapids, Iowa, assignor to Pettibone Mulliken Corporation, Chicago,111., a corporation of Delaware Filed Dec. 21, 1964, Ser. No. 419,978Claims. (Cl. 241-186) This invention relates to a hydraulic mechanismcomprising an improved device for operating the dust curtains of ahammermill or the like; this disclosure thereof being offered for publicdissemination in the event adequate patent protection is granted.

It has long been the practice to provide reversible hammermills withdust curtains and to make the dust curtains jointly shiftable orreversible to assume appropriate positions for each direction ofrotation. Reversible hammermills are commonly fed through a chuteextending directly upwardly from the highest point of the hammer circle.Viewed in cross section, the entering material such as rock, coal or thelike, or the fragments resulting from initial impact with the hammers,will be thrown .to the right with clockwise rotation of the rotor orhammers and thrown to the left with counterclockwise rotation. It is,therefore, desirable that the rigidly and permanently located breakerbars in both directions be spaced from the hammer circle to provide aclearance to receive this stream of fragmented material impelled byWithout such a clearance there would be excessive abrasion and wear, andin some instances, more fines than desired.

When the stream of fractured rock is being thrown through the clearancein one direction from the feed and impact area, unless a dust curtain ismoved into position across the opposite or idle clearance, dust will beswept or blown up through it and excessive quantities of dust willescape through the feed chute. The dust curtain preferably extends closeto the hammer circle. It is,

therefore, necessary to shift, or switch, or reverse the position-of thedust curtains each time that the direction of rotation of the hammerrotor is reversed. Heretofore, there has been a variety of mechanicalmeans for reversing the dust curtains. Somehave been successful, butnone have been really satisfactory and trouble-free. According to thepresent invention, a hydraulic mechanism is provided for reversing thedust curtains. A hydraulic system not only avoids the exposed linkagesor the like which weresometimes the source of trouble, but also lendsitself to the development (even though a manual pump is used) of highoperating forces when needed. In its preferred form, the hydraulicsystem, by an exceedingly simple hydraulic scheme, ensures equal motionof all parts of the dust curtains. This equalized movement is importantin achieving maximum ease of operation and in being sure that no matterwhere the dust curtain is located when movement is terminated,

its spacing from the hammer circle will be uniform along the length ofthe dust curtain.

Additional objects and advantages of the invention will be apparent fromthe following description and from the drawings.

Designation "of figures FIGURE 1 is a fragmentary verticalcross-sectional 3,245,623 Patented Apr. 12, 1966 "ice FIGURE 4 is a viewshowing a modification of one part of the hydraulic system.

Background description Although the following disclosure offered forpublic dissemination is detailed to ensure adequacy and aidunderstanding, this is not intended to prejudice that purpose of apatent which is to cover each new inventive concept therein no matterhow others may later disguise it by variations in form or additions orfurther improve ments. The claims at the end hereof are intended as thechief aid toward this purpose, as it is these that meet the requirementof pointing out the parts, improvements, or combinations in which theinventive concepts are found.

The invention has been illustrated in conjunction with a reversiblerotary crusher of the hammermill type. The details of this hammermillare not important to this invention, for the most part, and thereforeare not described.

Rotor 12 carries hammers 13 which are illustrated as mounted on swingarms 14. As the hammers 13 rotate their tips describe a hammer circle16. Material to be crushed is fed through feed chute 17. As it is struckby hammers 13 it is usually fractured and is thrown in the direction ofrotation. Clearance 18 between the hammer circle and liner or breakerplates 19 is desirable when the rotor 12 as viewed in FIG. 1 is rotatedcounterclockwise. An identical clearance 18 is provided in the oppositedirection because rotor 12 is reversible and this clearance is desirablewhen the rotor rotates in the. clockwise direction. Unless thisclearance is substantially closed off, excessive dust escapes throughfeed chute 17. Accordingly, it is desirable to have either clearance 18or clearance 18 closed off, depending on which is the direction ofrotation of the rotor. In other words, the idle clearance, which is notbeing used to receive the entering stream, should be blocked off by adust curtain. Dust curtains 21 and 22 can each be raised and lowered,and are preferably jointly operated. In FIG. 1, dust curtain 21 has beenshown raised, leaving entry clearance 18 open, while dust curtain 22 hasbeen shown lowered, blocking off the idle entry clearance 18'.

General description of present invention According to the presentinvention, the two dust cur tains 21 and 22 are reversed (one raisedwhile the other is lowered) hydraulically, in a system ensuring parallelmovement, or at least proper final positioning. In FIG. 1, a hydrauliccylinder 23 having a piston rod 24 is shown connected to an ear 26 ondust curtain 21. Likewise, a hydraulic cylinder 27 with piston rod 28 isshown connected to an ear 29 on dust curtain 22. These hydrauliccylinders are double-acting, so that they can exert a positive loweringforce as well as a raising force. It is easy to understand that dustcurtains in such an environment may become somewhat stuck in their upperpositions. As seen in FIG. 2, each dust curtain is provided with twohydraulic cylinders, one for each end thereof; Thus, the dust curtain 22is provided with a cylinder 31 having a piston rod 32 connected to car33 at the opposite end of the dust curtain 22 from the car 29. In FIG. 3all four cylinders are represented, cylinder 36 being connected bypiston rod 37 to the left end of dust curtain 21'.

The preferred hydraulic circuit is also shown in FIG. 3. A pumpv 41draws hydraulic fluid from a reservoir or tank 42. For reasons ofeconomy, the pump 41 is preferably a manual pump. A valve'43 has threepositions .and is operated manually, with a spring detent to hold it inany of the three positions. In the position shown it holds the dustcurtains 21 and 22 in any position in which they are found, blocking theflow of oil from all cylinders. Its other positions will either raisedust curtain 21 and lower dust curtain '22 or vice versa. The preferredbydraulic circuit is a single series circuit described further belowwhich has the advantage of ensuring equalized parallel movement of thetwo dust curtains, or all four ends moving equally.

As seen in FIG. 1, piston rods 24 and 28 carry actuators 46, which mayhe adjustable as shown, for tripp ng switches 47. These switches 47 areconnected to the motor control relay box 48 which includes reversingcontrols for motor 49 which is the drive motor for rotor 12. When dustcurtain 21 is raised, its associated switch 47 automatically controlsthe motor control 48 to cause rotation to be normally in thecounterclockwise direction. When dust curtain 22. is raised, itsassociated switch 47 controls motor control box 48 to cause the motor 49to drive rotor 12 normally in the clockwise direction. Preferably, ifneither switch 47 is actuated by a raised dust curtain, the motorcontrol unit 48 will not permit normal drive of the rotor 12 in eitherdirection. Of course, there may be overriding manual control so thatwhen desired, as for repair, the rotor 12 can be turned or inched ineither direction at any time.

Hydraulic circuitry The first installation of hydraulic dust curtainsused a more ordinary hydraulic circuit than that shown in FIG.

3, and was found to be troublesome in its failure to maintain parallelmovement of the dust curtains. Various means for obtaining parallelmovement were considered,

.but for reasons such as cost, none seemed quite satisfactory until theproblem was solved by the hydraulic circuit shown in FIG. 3. Theillustrated form of series hydraulic circuit solved the problemcompletely.

When the concept of a series hydraulic circuit was first considered, itwas discarded because of the unequal effective cross sections of the twoends of ordinary hydraulic cylinders, meaning, of course, the hydrauliccylinder and piston combination. Thus, referring to cylinder 36 in FIG.3, it is apparent that above the piston 36' the effective area of thepiston or of the cylinder is the full horizontal cross-sectional area ofthe cylinder 36. Below the piston 36, however, the eifective area isreduced by the cross-sectional area of the piston rod 37. 'It follows anattempt to move both ends of dust curtain 21 equally by a seriescircuit, considering its two cylinders only, would fail. Thus, if pumppressure should be applied below piston 36' to raise that end of thedust curtain 21, and the upper end of cylinder 36 connected to the lowerend of cylinder 23 to raise that end of dust curtain 21, the unequalcross sections above piston 36' and below piston 23 would cause piston23' to be raised faster than piston 36.

According to the present invention, however, all intercylinderconnections are to cylinder ends of equal effective cross section.nected from the valve port to the upper end of cylinder 31, the lowerend of cylinder 31 will be connected not to cylinder 27. but to thelower end of cylinder 36. Now thepiston 36 will be raised the sameamount that the piston 31' is lowered. The upper end of cylinder 36 isconnected to the upper end of cylinder 27, both being a full crosssection. Therefore, piston 27' will be lowered the same amount thatpiston 36' is raised and hence the same amount that piston 31' islowered. The lower end of cylinder 27 is connected to the lower end ofcylinder 23, and thus its piston 23' will be moved the same amount asthe other three pistons. The other valve control line 52 is connected tothe upper end of cylinder 23.

It would usually be desirable to have the pump and valve unit 41, 43located considerably below the cylinders. In that event, there will be atendency for the hydraulic fluid in line '51 or 52 to run out if theconventional fully open return connection is provided through valve 43.Ac-

Thus, if a valve control line 51 is con-.

cordingly, relief valve 61 has been provided in the return line fromvalve 43 to tank 42. This is a low pressure relief valve having thepurpose of merely maintaining above it enough pressure to overcome thegravitational pressure of the oil in line 51 or line 52. A pressurevalve maintaining 65 pounds per square inch has been chosen because ofready commercial availability and to provide a safe margin. Commercialunits including pump 41, valve 43 and tank 42 conventionally include ahigh pressure relief valve 62. The pump 41 is capable of producing highpressure, even though manual, and a relief valve 62 which limits theline pressure to 2,000 pounds per square inch is deemed suitable anddesirable. In one commercial embodiment, 400 pounds per square inchseems adequate, and hence the 2,000 pounds is expected to overcome anyincreased friction or binding by particles.

It is desirable that all air be eliminated from the hydraulic system.The conventional bleed plugs 70 are an aid to this end. However, a bleedreservoir 71 is preferably connected to the uppermost point of everyintercylinder hydraulic line, the bottom of the reservoir being higherthan any point it supplies. Each is connected through a valve 72 whichwill normally be kept closed so that the system will function as if thebleed reservoir 71 were not present. 'During installation, however, orwhenever the presence of air is suspected, the appropriate valve 72 canbe opened allowing any air which has accumulated below the valve to flowup into bleed reservoir 71, being replaced by oil from that reservoir.During installation, before the dust curtains are installed, air is bledrepeatedly while alternate pistons are held up to allow the right amountof oil to enter. After installation, it bleeding is necessary, the rightamount of oil can still be allowed to enter by raising the dust curtainwhich is too low. If this proves necessary unexpectedly often, eachreservoir may be provided with a valve nipple 73 through which air oroil may be inserted into the reservoir to hold the raised piston at theproper level until valve 72 is closed. Instead of reservoirs 71, theremay be simple bleed valves with provision for connecting temporarily asource of oil under pressure.

FIG. 4 shows a modification of the hydraulic circuit which is possiblebecause the contents of the hydraulic circuit are constant insofar asoperation is concerned. Here the pump 41 is connected between the portsof the valve, no sump tank in the ususal sense being provided. Tomaintain a pressure in the discharge line safely, a small reservoir 81may be provided at a level above all cylinders. This reservoir will alsotake care of expansion of oil in the system. It is only with this systemthat reservoirs 71 may be needed for lines 51 and 52; and probably theywill not be needed then if reservoir 81 is provided.

Pump 41 preferably uses a small piston suitable for developing 10,000pounds pressure per square inch by manual operation. This makesoperation at the expected 2,000 pounds per square inch very easy. Moreimportant, it facilitates delicate adjustment of the position of thelower dust curtain, a full stroke only moving it about one thirty-secondof an inch. Nevertheless, the entire pumping operation takes only aroundhalf a minute.

Further details Some operators will prefer to adjust actuators 46 toactuate switches 47 only as the dust curtain being lowered reaches itsdesired position. Other operators will prefer an adjustment actuatingswitches 47 enough earlier so that actuators 46 will never needadjustment, but will actuate switches 47 by the time the lowering dustcurtain reaches any of the positions that may be desired. For thelatter, switches 47 should tolerate further movement after they havebeen actuated.

It may be desirable to provide at one or more intermediate points alongthe length of dust curtains 21 and 22, clamps 86, as seen in FIGS. 1 and2. Each clamp may have welded to it a spacer heel 7 and a bolt 88. Theclamps may be held in proper position by guide strips 89 Welded to theadjacent Wall member. The nuts on bolt 88 may be more accessible if aspacer 91 is provided. It will usually be preferred to adjust the nutsso that dust curtains 21 and 22 can slide smoothly and easily, but ifobjectionable rattles should develop the nuts may be taken up after eachreversal of the dust curtains to stop such rattle.

The dust curtains may have the simple construction seen in FIG. 2, inwhich a tie plate 92 is welded to each end of the main horizontallyextending section of the dust curtain each being secured by bolts 93 toan end plate 94, these end plates bearing the ears 29 and 33. Thisfacilitates assembly and also permits ready replacement of the mainportions of the dust curtains which may wear fastest.

Customary side liners 96 provided within the housing of the hammermill11 at the ends of the rotor may be shaped to form slots 97 into whicheach dust curtain slides. The seat of this slot could serve as a stopfor the movement of the dust curtain toward the hammer circle. However,it is preferred that this slot extend somewhat too deeply for new unwornhammers, and hence the positioning of the dust curtains will usually bechosen by the operator. Of course, he will choose a position which isnot struck by the hammers, but which is close enough to the hammercircle to accomplish the desired or achievable reduction of escape ofdust. T urnbuckles or threaded adjustable tubes 98 may be providedbetween the piston rods 24, etc., and clevises 99 which are pivoted toears 26, etc. to adjust the lowest length to which the dust curtainswill extend. This is believed not to be necessary, however, in view ofthe ease of obtaining accurate positioning of the dust curtains by thehydraulic system of this invention.

With this invention, the reversing of the positions of the dust curtainsis accomplished very easily, and they can be very accurately positioned.Enough force is available for very dependably and easily overcoming anyjamming which may occur from lodged particles of the material beingcrushed.

What is claimed is:

1. Apparatus for reversing the positions of two dust curtains onreversible hammermills and the like including four double-actinghydraulic cylinders with pistons, and piston rods extending in onedirection only from the pistons and reducing the elfectivecross-sectional area of the cylinders in that direction from thepistons; each linked to a different one of the four end portions of thetwo dust curtains; a hydraulic pump, and a three-position valve andconduits for at will supplying pump pressure above the pistons of onedust curtain and below the pistons of the other dust curtain, or viceversa, or locking the pistons in their given positions by blocking allflow from the cylinders; said valve being connected to said cylinders ina series circuit with each intercylinder connection being betweencylinder ends of the same elfective cross-sectional area whereby allpistons move equally.

2. Apparatus for reversing the positions of two dust curtains; ahydraulic pump, and a three-position valve and conduits for at willsupplying pump pressure above the pistons of one dust curtain and belowthe pistons of the other dust curtain, or vice versa, or locking thepistons in their given positions by blocking all flow from thecylinders; said valve being connected to said cylinders by a serieshydraulic circuit extending from a pressure port of the valve to a givenside of cylinder one connected to dust curtain A, from the same cylinderon the opposite side of the piston to the like end of cylinder twoconnected to dust curtain B, from cylinder two on the opposite side ofits piston to a like end of cylinder three, connected to dust curtain A,from the opposite end of cylinder three to the like end of cylinder fourconnected to dust curtain B, and from the opposite end of cylinder fourto the return port of the valve.

3. Apparatus for reversing the positions of two dust curtains onreversible hammermills and the like including four double-actinghydraulic cylinders with pistons, each linked to a different one of thefour end portions of the two dust curtains, a hydraulic pump, and athree-position valve and conduits for at will supplying pump pressureabove the pistons of one dust curtain and below the pistons of the otherdust curtain, or vice versa, or locking the pistons in their givenpositions by blocking all flow from the cylinders; said valve beingconnected to said cylinders in a series circuit with each intercylinderconnection being between cylinder ends of the same effectivecross-sectional area whereby all pistons move equally.

4. Apparatus for reversing the positions of two dust curtains ofreversible hammermills and the like including four double-actinghydraulic cylinders with pistons, each linked to a different one of thefour end portions of the two dust curtains; and a hydraulic system foractuating said cylinders including hydraulic pump means, and athree-position valve and conduits for at will supplying pump pressureabove the pistons of one dust curtain and below the pistons of the otherdust curtain or vice versa, or locking the pistons in their givenpositions by blocking all flow from the cylinders, said hydraulic systemincluding means to cause each dust curtain to move with parallelmovement.

5. Apparatus for reversing the pistons of two dust curtains onreversible hammermills and the like including four double-actinghydraulic cylinders with pistons, each linked to a different one of thefour end portions of the two dust curtains, hydraulic pump means, and athreeposition valve and conduits for at will supplying pump pressureabove the pistons of one dust curtain and below the pistons of the otherdust curtain, or vice versa, or locking the pistons in their givenpositions by blocking .all'flow from the cylinders, said apparatusincluding means for ensuring for each dust curtain, when lowered, properangularity as to the hammermill.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS1/ 1940 Great Britain.

EDGAR W. GEOGHEGAN, Primary Examiner.

1. APPARATUS FOR REVERSING THE POSITIONS OF TWO DUST CURTAINS ONREVERSIBLE HAMMERMILLS AND THE LIKE INCLUDING FOUR DOUBLE-ACTINGHYDRAULIC CYLINDERS WITH PISTONS, AND PISTON RODS EXTENDING IN ONEDIRECTION ONLY FROM THE PISTONS AND REDUCING THE EFFECTIVECROSS-SECTIONAL AREA OF THE CYLINDERS IN THAT DIRECTION FROM THEPISTONS; EACH LINKED TO A DIFFERENT ONE OF THE FOUR END PORTIONS OF THETWO DUST CURTAINS; A HYDRAULIC PUMP, AND A THREE-POSITION VALVE ANDCONDUITS FOR AT WILL SUPPLYING PUMP PRESSURE ABOVE THE PISTONS OF ONEDUST CURTAIN AND BELOW THE PISTONS OF THE OTHER DUST CURTAIN, OR VICEVERSA, OR LOCKING THE PISTONS IN THEIR GIVEN POSITIONS BY BLOCKING ALLFLOW FROM THE CYLINDERS; SAID VALVE BEING CONNECTED TO SAID CYLINDERS INA SERIES CIRCUIT WITH EACH INTERCYLINDER CONNECTION BEING BETWEENCYLINDER ENDS OF THE SAME EFFECTIVE CROSS-SECTIONAL AREA WHEREBY ALLPISTONS MOVE EQUALLY.